There are three major trends that can be observed in photovoltaic market: lower hardware cost, need for soft cost drop and need for design optimization.
As a result of the latter one, traditional design rules don’t apply to every project anymore. Designers started to put more stress on power density (more modules installed) than energy density (highest energy output per module).
Playing with energy density and power density includes optimization of inter-row spacing, tilt, azimuth or inverter type, etc. Softwares like EasySolar app let designers run a lot of simulations to compare different scenarios and choose the best one.
In many cases, the type of inverter used, determines PV design. In case of applying module-level optimization (microinverters, optimizers), modules can be designed closer to shade, or where the shade occurs only in winter, which increases power density.
Inter-row spacing and inclination
Sometimes inter-row spacing is reduced and tilt is minimized to keep modules closer together. If modules are more packed, the rooftop area has more solar power available. East-west mounting favourizes this solution.
Most of rooftops do not face south, so sometimes solar designers prefer to align modules in the direction of the building so that more modules can fit in the roof. It also looks more aesthetic which remains important for residential projects.
To simulate different design scenarios go to EasySolar app.